Pliers for crimping workpieces are commonly known. Usually, the pliers are used to connect electrical connectors to the end of an electrical conductor. But it is also possible to use the present invention for other pliers or scissors.
It is essential to the invention that two crimping dies and two mounting dies are provided, at least one of the two crimping dies being replaceably arranged at the corresponding mounting die. The invention is especially directed to pliers in which the mounting dies and the crimping dies connected to the mounting dies are pivoted. This means that the mounting dies and the crimping dies are moved in a scissors-like movement toward and away from each other. The present invention is also applicable for pliers in which the mounting dies are linearly moved toward and away from each other.
Pliers are known from the brochure "Handzangenkoffer fur Fertigung und Service" of AMP Deutschland GmbH, issue 1997. The pliers have a hand drive including two pivotable handles or levers. The handles transfer their movement to mounting dies, one crimping die being replaceably arranged at each mounting die. Each crimping die includes a support step which is allocated to a linear edge portion of the corresponding mounting die. The crimping die with its support step is supported on the linear edge portion of the mounting die. The crimping force is transferred to the crimping die by this support step. The support step has to be produced in an additional processing step. Usually, the support step is produced by a milling cutter to attain the necessary tolerances. This is true for a plate arrangement as well as for cast crimping dies. The crimping die includes a flange which in its mounted position does not extend beyond the outline of the mounting die. A freely protruding portion is connected to the flange, the portion, for example, being provided with dies or other tools. The support step is located the region between the flange and the portion. Bores are provided in alignment in the mounting die and in the flange of the crimping die to affix the crimping die to the mounting die. A fixing screw is inserted into the bores with a clearance and it is tightened. It is advantageous that the crimping die is easy to replace by unscrewing the fixing screw. Additionally, the power is transferred by a relatively large support step. Usually, the mounting die includes two parts, so that a support step is arranged on each side of the crimping die. It is disadvantageous that the support steps have to be processed by a milling cutter, or, using cast crimping dies, that the support step has to be formed in the cast form with a certain precision. The crimping die itself may include several plates having different dimensions corresponding to the depth of the die. When the crimping die is loosened or replaced, the plates fall apart, so that there is a likelihood of mixing up the plates by mistake. Especially in case of pliers using a scissors-like movement of the mounting dies, the mounting dies tend to shift from the joint connecting the mounting dies to the outside, so that the mounting die is dislocated by the support step sliding on the corresponding edge portion of the mounting die. The shifting movement is limited by the clearance of the fixing screw. Such a shifting movement leads to a change of the crimping point, and has a negative effect on the crimping preciseness. The threat of the fixing screw is not suitable for a stop limiting the shifting movement.
It is known from the above cited brochure to prevent the shifting movement by mounting the crimping die to the mounting die using pins. Two bores are arranged in the flange of the crimping die, and the mounting die includes two corresponding bores arranged in alignment. Two pins are inserted with force into the circumferentially closed openings or bores in the mounting die and in the flange of the crimping die. The pins are mounted in the flange of the crimping die with a press fit, as well as in the mounting die. Additionally, bores are arranged in the flange of the crimping die and in the mounting die, the fixing screw being inserted into these bores with a clearance. The fixing screw is necessary to affix the elements and to pull them together. The advantage of using a pin is that the crimping die does no longer tend to shift, and that an exact relative position of the crimping die with respect to the mounting die is ensured, considering the processing tolerances. Thus, the processing quality is improved. In case it is possible using the pins, the support surface serving to transfer power is advantageously enlarged by a double fit additional to the support step. The embodiment using pins may be also used if the crimping die does not include a support step. In this case, the support surface formed by the two pins exclusively transfers the power. It is disadvantageous in these known pliers that it is rather difficult to replace the crimping die, which requires the driving out the pins after loosening the fixing screw. The processing of these pliers is comparatively complicated. A certain precision has to be attained with respect to applying the bores considering the tolerance.
Pliers are also known from the German Patent Application DE 37 17 130 A1. One crimping die is replaceably connected to each mounting die. One screw and two pins are provided extending through the aligned openings located in the corresponding mounting die and in the corresponding crimping die. In case the pins are arranged in the openings with a press fit, the shifting of the crimping dies from the joint connecting the mounting dies to the outside is prevented, so that the crimping dies cannot slide on the support step located on the corresponding edge portion of the mounting die. This arrangement does not allow a fast and simple replacement of the crimping dies.
Furthermore, cast crimping dies are known, the crimping dies including a cast support step. The mounting die and the flange of the crimping die are also connected to each other by a fixing screw extending through these elements. Additionally, two bores are arranged in the mounting dies, and one bore is arranged in the flange of the crimping die. Only one of the bores arranged in the mounting die is used by a pin being driven into the bore. This pin and the support step located at the crimping die transfer the power, so that there is no likelihood of shifting of the crimping dies. On the other hand, it is difficult to attain a coordination of the support step with respect to the driven in pin considering the tolerances. The known pliers which serve to crimp isolated electrical connectors include a mounting die having a circumferentially open semicircular recess. A semicircular protrusion arranged at the support step engages the recess with a clearance. This arrangement only prevents a mixing up of the crimping dies during insertion into the mounting dies. The semicircular recess does neither have an influence on the transfer of power, nor on the shifting. Anyway, the semicircular recess is only arranged on one of the two mounting dies.